Hydraulic brake system



C. SAUZEDDE June 27,' 1939.

HYDRAULIC BRAKE SYSTEM Filed July 8, 1935 ww w Patented June 27, .1939

2,163,633 `n YImArJLIc BRAKE SYSTEM claude sumada, Detroit, nnen., assigner to troit Hydrostatic ,Brake Gorporation, Det it.

'* UNITED -s-'ra'rlezsl Mich., a corporation of Michigan Application July 8,1935, serial No. 30,232- s claims. (ci. nus- 152)- The present invention relates to hydraulic brakes for automotive vehicles, aircraft andthe like. 1

` The primary object .of the present invention is to provide means for maintaining an adjusted relationship between the brake shoes and the v braking surfaces in hydraulic brake systems and,

to avoid .the necessity of readjustlng the brakes when temperature conditions cha ge. It is well 10 known that in certain we ll known types oi hydraulic brakes the relationship between the brake shoes and the braking surfacesmust be adjusted to compensate for volumetric changes in thc liquid of the system resulting from expansion or con apply or partially applythe contracts itresults in a lost-motion connection brake shoes. The invention automatically compensates for either expansion or contraction of thev liquid and permits the brakes to function nor-- mally under various temperature and'climatic 25 conditions..

the system thesystem is automatically -repleri` ished by 1iquid -fromv the auxiliary chamber.

With the above-and other ends in view the in- 40 vention is fully disclosed by way of example in the following description, reference being had to the accompanying drawing, in which Fig.- 1 is a diagrammatic illustration of the brake system;

Fig. 2. is a horizontal cross section of the pressure member; I

Fig. 3 is a side elevation of thepressure member.

and I Fig. 4 is a view. partly'incrosssection, of a- VLike characters of reference are employed throughout to designate corresponding parts. Referring more particularly to Fig. 2 the inventicncompri'ses a means 'for manually applying pressure on liquid in a'brake system. The prestraction of the liquid dueto temperature changesresulting from changing 'climatic conditions. when the liquid-expands it has a .tendency -to v brakes and when it between the pressure applyingmember and the Another obiect Aof the present invention is tov sure means is generally designated by the numeral I. It comprises a body formed with two cylinfdrical chambers 2 and 3, the axes of the chambers being made parallel for convenience in manufacture and assembly. One end of eachchamber is 5 closed by an'end wall 'I and 5 respectively, the wall 4 having a port 6 to which a conduit 1 is connected and the wall 5 having a port 8 to which a conduit 9 is connected. As shown in Fig. 1 the conduit 1 ,has branches I0 leading to the two rear brakes m and the conduit 9 has two branches I2 leading-t0 5 the two front brakes I3 of 'anautomobile brake system.

Shoulders are formed at the ,other ends of the chambers- 2 and 3 and internally threaded annular 15 parts I8 surround the shoulders. Il and receive externally threaded elements I6. Flanges |1\on flexible seals I8 are tightly interposed between the ends of the elements I8 and the shoulders Il and in the seals I8 are supported metallic plungers I9. 20

' Movement of the lplungers I9 in` their respective chambers is limited lby engagement with shouldersl 2l formed in the elements I8.

Extending through axial bores in the elements I8 are rods 2| and 22.` -One end o f the rod 2| 25. engages-the plunger |9 in the chamber 2 'and one end of the rodl 22 engages the plunger I9 in the *chamber 3. The ends of the rods 2| and 22 which extend outwardly of the elementsV I8 are connectedby a cross link 23 having an angular aper- 3o ture 2l therein. A foot pedal 2 5 adapted to be pivotally supported in a vehicle in the usual man-S ner has an angular-part 26 extending through the aperture 24.

When the plungers I9l are in their normal lor 35 inoperative position their end s will'be in engage- "ment with the shoulders 20 and their other endsv will be spaced fromthe end walls l andi substantially as shown in Fig; 2. The side walls of the chambers 2 and 3 are provided with radially. o extending ports 21 and 28 disposed, as regards to the length of the chambers, so 4that they are not covered bythe seals VI8 Vor plungers I9 when the "latter -arein their inoperative position and so that upon a slight movement of the plungers, as will be 45 hereinafter more particularly described. both ports 21 and 28 willbe covered.

The ports 21 and 28 communicate withpassages 29 in annular bodies 38 having caps 3| formed with flanges 32. The annular bodiesJ 29 have their wallbent over'to engage the anges 32 to permanently secure the caps 3| with respect thereto. 'A double cupped seal 33 is provided in each of the bodies 2'9 and each seal has a flange 34 tightly interposed between the flanges '32 and thev 55 respective bottoms of the annular bodies 29. The seals 33 are reinforcedl by metal cups 35 and coil springs 36 are compressed between the cups 35- and their respective caps 3 I. 5 In order that the function of the invention may\ be more readily understood there is illustrated a hydraulic brake of a type with which the invention has particularfutility. The brake is shown in'Fig. 4 in which the numeral 31 designates a spider splined on an axl'e 38. The spider has a plurality of annular recesses 39 and passages 40 interconnecting the recesses and also connecting them to a main supply conduit 4I and to an air bleeder valve 42. In each recess 39 is a plunger 43 and a flexible sealing member 44. The plunger 43 supports an adjustable element 45 which engagesa bracket 46 supporting brake shoes 41. In the illustration two sets of shoes 41 are provided and they are connected by springs 48 which func- 24)- tion to retract the shoes and to move the plungers 43 inwardly of the annular recesses 39. In the event that uid under pressure is supplied in the conduit 4I the plungersA 43 and shoes 41 will be moved outwardly and into contact with the brak- 25 ing surface which is diagrammatlcally represented by the line 4,9. For an understanding of the invention it will be assumed that one of the branches I0 or I2 is connected to the conduit 4l and that the remaining conduits are connected to au similar conduits in similar brakes. 'c

When the pedal 25 is moved throughapplication of manual ,pressure thereon the part 26 en gages a side wall of the aperture 24 and moves the connecting member 23 and rods 2l and 22. Movement of the rods 2| and 22 pushes the plungers I9 toa position where the seals I8 cover the ports 21 land 28 and continued movement after the ports 21 and 28 are covered moves the liquid from` the chambers 2 and 3 into the conduits 1 and 9. The liquid is thus supplied under pressure to the conduit 4I with the result that the plungers 43 move the shoes 41 outwardly and into engagement with the braking surface 49. The brakes are thus applied. Y Y 45 As will be seen by a comparison of Figs. 2 and 4, the piston chamber of the piston and cylinder assembly of the actuator mechanismis in permanently-open communication with the conduit 4I and through conduits 40 with the chamber of the brake applying elements. Hence, movement of the brake pedal-counter-clockwise in Fig. 3 will serve topfo'rce uid from the piston chamber into the channel connections and thus shift the piston for the brake-shoe operation in the direction to apply the brakes. When the brake pedal is released, the springs 48 become active as a power source',- tending to move the brake shoes inward and away from braking contact, thus causing the piston of the unit to drive fluid from the unit piston chamber into the connections and thus b'ack into the piston chamber of the actuator mechanism.` During the brake-setting movement lthe pedal pressure is obviously greater than the pressure ofsprings 49, but when the pedal is released, the springs 48 provide the power pressure since the brake pedal does not then set up an opposing-pressure; when the p edal pressure is released.' by the operator, he loses control of the returning movementexcepting that it is possible 7o for him to provide a gradual release ofV braking i pressurevby preventing pedal movement `by the power of springs 48 by retaining his foot on the `pedal instead of denitely removing it;so thatV the release can be controlled in this way, if desired. n

, In other words, the fact that the piston 'chamber o f the actuating mechanismand that of the unit carrying the brake-applying element are in open communication. with the pedal control active only as a possible retarding member vduring the brake release movement, tends to retain the uid of the chambers and connections under substantially constant pressure of a denite value, with the fluid acting in the nature of a mobile piston.- This is made possible by the fact that the port communication with the auxiliary supply means, represented by 30, is open to the piston chamber of the actuating mechanismonly when the piston I9 is substantially in its inactive position. As soon as the piston advances a suiilcient I distance to close this port communication, the

, volume of the mobile piston becomes fixed in amount, so that further advance of the piston is against the'power of the springs 48, and since the volume cannot then be changed, the pressure applied to the brakefshoes is the excess applied tothe pedal over the resistance of springs 4B.

However, when the piston is in its inactive position, as in Fig. 2, the port communication is' open to the auxiliary supply chamber 30, thus bringing into activity the power of spring 36of less power than springs 48./ This brings intol action a number of conditions. For instance. assume that the brake application has been such that considerable heat has been developed,and 'thatsuch he'at has resulted in a slight expansion of the fluid; as long as the brake pedal carries the excess power the fluid expansion would be eifective as against either the pedal or the brakeapplying piston. or both; when, however, the pedal is released, springs 48 become active to move the mobile piston in the opposite direction, and since the expansion has tended to increase the space required for the fixed volume, the piston will reach its port-opening position before the brake-element piston has reached its inactive position, so that the respective powers of thetwo sets of springs 36 and 48 become active-as spring 48 has the greater power the excess fluid will pass .into the supply chamber: should the fluid cool while i n this position and thus tend to decrease the space required, spring 36 becomes active to restore the volumeof the mobile piston to that which is set by the power of spring 3G. springs 48 preventing yielding ofthe brake-applying piston duringrv this compensation action. due to the superiority of power of springs 48. Hence. when the next brake application takes placecthe volume of the mobile piston will be that which has been set. Y Y

If there has been no expansion of the mohile piston. opening of the port to thel supply chamber will not vary the volume unless the pedal should have, at such time,`a greater power than spring 36-if the pedal is released. its power is less than that of spring 36 and since the volume is the same as. when the porthad been closed at the beginning of the brake application. it will remain constant and the supply chamber is unad'ected. .Since the port remains ppen excepting during a particular brake application, normal tempera- This is made possible through the -fact` that the system ,is itself sealed into what may be termed a "closed system, in that all points where it would 10 be possible for air to leak into or out of the fluid flow path are completely sealed by the several sealing structures disclosed, so far as involuntary supply or discharge is concerned; provision is made to bleed the system of air on initial filling,

or when replenishing a supply, as in the case of accident, but such condition is a voluntary action, with the operator having knowledge of the condition and therefore able to remove the air through the safety valve 42. In other words, ad-

mission or even seepage of air into the flow pathofthe iluid is prevented by completely sealing all vulnerable points. With this condition present,

and the superiority in power of springs 48 over spring 36, and the superiority in power of the latter over the inactive pedal,` ensuring that the actuator piston will return to its inactive position 'and thus limit the dimensions of the actuator piston chamber, change in volume, except as indicated, and the development of suction condi- Ytions whichvwould tend to cause air to seep into the flow path, are eliminated.

Although a specic embodiment has been illustrated and described it will be understood that various changes may be made within the scope of the appended claims without departing from the spirit of the invention, and such changes are contemplated.

.what I claim is:

l. In hydrostatic braking systems, wherein each j unit to be brakedearries brake-applying elements `movable to brake-applying position by uid pressure and away from such position by spring pressure, and wherein actuator Imechanism includes ments while maintaining open communication between the piston chamber of the actuating mechanism and the brake applying elements, said control means including a variable'uid storage chamber with the chamber iluid under spring pressure of less value than the spring pressure value operative to move the brakes away from applied position, said means also including port communication between such storage chamber and the piston chamber of the mechanism with the portage forming the sole communication between the chambers, said port communication being controlled as to activity and inactivity solely by the piston functioning as a portage cut-off and with communication activity limited toY periods when the piston is substantially in its inactive a piston and cylinder assembly for providing a position to thereby limit changes in the volumetric value of the active fluidcontent of an individual braking activity to the period between the closeof one activity and the beginning of the succeeding activity tov cause successive brakl ing activities to be provided under equal volumetric value conditions, change-compensating activities being provided by the differential in pressure between the spring pressures respectively active in returning the brakes and in the means providing chamber fluid pressure and with the differential activity limited to the period between successive braking activities.

2. A system as in claim 1 characterized in that means are provided for sealing the actuator mechanism, the brake-applying elements and the fluid connections therebetween against involuntary influx or escape of air to the fluid content of y the system.

3. A system as in claim 1 characterized in that the port communication between the storage chamber and the piston chamber is controlled as to activity and inactivity by a cylinder-contacting wall of the piston.

4. A system as in claim 1 characterized in that the port communication between the storage chamber and the piston chamber extends to the inner face of the piston cylinder wall, whereby the advancing movement of the piston within the cylinder from its inactive position serves to close such portv by a peripheral wall of the piston.

5.' A system as in claim 1 characterized in that the cylinder assembly includes a stop formation co-operative with the piston to limit the stroke of thepiston in the direction of brake-release movement, the wall of the cylinder carrying the cylinder entrance of the port communication with the storage chamber at a point where the piston will unclose such entrance as it closely approachessuch stroke-limit posit on.

6. A system as in claim 1 char cterized in that the piston and cylinder formation, the storage chamber formation, and the brake-applying element formation each include an expansible seal structure effective to isolate the flow-path of the fluid against involuntary inuxand discharge of air to or from such flow path, whereby a closed system is provided.

"7. A system as in claim 1 characterized in that Vthe piston and cylinder formation, the storage chamber formation, and the brake-applying elements each include an expansible seal structure anchored to a non-movable portion of the formation with which it is associated, said seal structures being effective to isolateV the Sw-path of the fluid against involuntary inux and discharge.

of air to or from'such flow path. Y

8. A system as in claim 1 characterized in that the piston and cylinder formation, the storage chamber formation, and the brake-applying element formation each include an expansible seal structure effective to isolate the flow-path of the iiuid against involuntary influx and discharge of air to or from such'fiow pathaneans being provided to provide voluntary discharge of air to the 'ilow path at will.

IcLl'iUnE sAnzEnDE. 

